Various conventional sealing efforts for aircraft door structures still leave such doors as a weak spot in terms of thermally insulating the aircraft cabin from the exterior. Thermographic images have shown that the doors constitute such weak spots. Especially door sections near the cabin floor have low surface temperatures when an aircraft is flying at high altitudes through an extremely cold environment. Such low temperatures of the inner door surface and of the door frame particularly near the cabin floor are unpleasant for passengers and crew. Due to these cold surface temperatures the circulation inside the aircraft is adversely affected near the doors because a cool draft is formed just above the cabin floor due to a convection flow downwardly along the inner door surface. Thermal seals between the door and its frame have so far not brought thermally satisfactory solutions of the above problem.
Separately and actively heating the aircraft doors is also not a satisfactory solution because such heating involves a substantial energy consumption which should be avoided if possible in view of the extra fuel consumption such separate heating would require. Moreover, door heaters with their sensors and controls would increase the initial and operating costs of an aircraft. Separate temperature sensors and controls would also increase maintenance work to assure that the door heaters work properly and independently of the cabin heating system.